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Myths and Facts about ADHD

Introduction

Major advances in the neuroscience of ADHD in the past two decades have altered medical understanding of this disorder. Moreover, these neuroscientific advances indicate that many of the previous medical and public beliefs about ADHD are no longer tenable. In this chapter we provide current information about developmental changes in ADHD and about causal factors in ADHD. These dispel previous beliefs that children "outgrow" ADHD by adolescence or that it is a new disorder attributable to today's crowded and fast-paced life, to the consumption of too much sugar, food colouring, or junk food, or to poor parenting. Undoubtedly, another decade of research will clarify some of the "uncertainties or unknowns" and may modify some of the current understanding presented here - this is the nature of the scientific process.

Children do not outgrow ADHD

Inattention and hyperactivity/impulsivity symptoms of ADHD vary across development (that is, between early childhood, adolescence, and adulthood). Contrary to common beliefs, children do not "grow out of" ADHD.

Between 60% and 80% of children diagnosed with ADHD will still have symptoms of the disorder in adolescence and adulthood. These symptoms can impair their functioning in social and occupational situations.1

Overt hyperactive/impulsive symptoms tend to be more prominent during preschool and early school age years but gradually lessen as the child enters adolescence. Instead, adolescents and adults may manifest their hyperactivity internally and report feelings of "inner restlessness." 2 Likewise, impulsive symptoms common to preschool and early school aged children with ADHD (for example, actively moving before thinking) may be displayed as verbal outbursts in adolescents and adults.

In contrast, symptoms of inattention (such as forgetfulness, disorganization, and difficulty concentrating) are persistent throughout development.3

Continuing symptoms of inattention are of particular concern because they are more strongly associated with cognitive, language, and learning difficulties than are hyperactive/impulsive symptoms (these findings will be expanded upon in Chapters 3 and 4). Individuals who experience symptoms of inattention, but who may never or may no longer meet full criteria for a diagnosis of ADHD, are likely to show levels of academic, occupational, and social impairment similar to children with a formal diagnosis.4-7 Thus, as depicted in Figure 2-1, ADHD is associated with impairments in many domains of functioning across the lifespan.8

Figure 2-1: Pervasive impairments associated with ADHD across the lifespan

 

ADHD changes across the lifespan

ADHD symptoms in infants

Although ADHD is a neurodevelopmental disorder, virtually nothing is known about its early onset and manifestation during infancy. This is because there is no specific diagnostic test for ADHD at any age, including infancy. During a child assessment for ADHD, parents often report that in infancy their child was "difficult to regulate and manage," or that the doctors had detected minor neurological problems in preschool years (for example, the child had problems with fine motor coordination). What is known at present is that:

  • Regulatory problems (such as irritability and sleeping and feeding problems) in infants do not necessarily lead to ADHD in early childhood, although they are often associated with a range of emotional and behavioural problems.9
  • The presence of minor neurological problems in the preschool years is associated with an increased risk for ADHD, which supports the notion that ADHD is a neurobiological disorder.10
  • Infants of fathers with ADHD show neurodevelopmental immaturity and some subtle cognitive problems, but it is not known yet whether these infants will grow up to have ADHD themselves.11

ADHD in preschool and kindergarten children

Teachers of preschool-aged children identify classroom behaviour problems, including those caused by ADHD, as important detriments to the daily functioning of the class and to student progress. It is estimated that about 2% to 5% of preschoolers meet criteria for ADHD.12 Although many doctors are reluctant to give a diagnosis of ADHD at this young age, there is growing evidence that early behavioural problems do not dissipate and that marked inattentiveness in preschools predicts later academic underachievement.5 13 For example:

  • Symptoms of inattention in kindergarten are associated with poor reading readiness skills. This in turn has a strong negative effect on reading abilities in the first grade.
  • Inattention in the first grade is predictive of reading underachievement, even when other factors are taken into account (such as kindergarten reading achievement, IQ, and parental involvement).

Preschool children with ADHD stand out markedly from their non-ADHD peers on a variety of behaviours and abilities:13-15

  • unable to sit through games, stories, and circle time; may roll around floor or crawl under tables
  • constantly asking questions but racing off before the answer is given
  • constantly running and on the go and stopping only when they collapse from exhaustion
  • seemingly unaware of preschool routines, rules, and expectations, even after several months in school
  • failing to meet academic and social expectations of preschool and kindergarten environments
  • cognitive weaknesses in working memory, inhibitory control, speed of processing information
  • problems in understanding the "instructional language of the classroom" and producing organized and focused spoken responses to teacher's questions
  • banging into objects and people, climbing and jumping off furniture
  • frequent injuries often requiring hospitalization (head injuries, fractures)

ADHD in school-age children

Although children with ADHD vary in the severity and types of problems shown at school, they typically stand out from their classmates in many ways. For example, in addition to showing the behavioural symptoms of ADHD described in Chapter 1, they:

  • generally act much younger than their age, despite having average intellectual ability
  • often act as the "class clown" and by so doing gain the attention of other children and disrupt their work — this is much more common among boys with ADHD16
  • talk excessively when they are not supposed to, but may become silent or monosyllabic when called upon by the teacher to respond17
  • often do not have any close friends or have difficulty reciprocating and sustaining friendships18-20
  • typically (but not always) have problems with their school work and homework despite good intellectual abilities (for example, not able to work independently, unable to start or to complete in-class work or homework)
  • often show great difficulty in or even avoid written work, so they write little or nothing down on paper21
  • often obtain lower academic achievement scores and are at high risk for failing the grade level, despite average intellectual ability6 8
  • are at increased risk for accidental injuries at school and home (particularly injures such as bone fractures, due to falls, bicycle accidents, and pedestrian accidents)22-23

Academic failure is more closely associated with the Inattentive and Combined subtypes of ADHD, whereas the Hyperactive/Impulsive subtype is most often associated with co-occurring oppositional behaviour and conduct problems, but not academic problems.5 7 24 Thus, it appears that the dimension of inattention (common to both Inattentive and Combined subtypes) is what predicts poor academic outcome.

ADHD in adolescents

Adolescence is a developmental stage in which risk-taking and rebellion are considered normal behaviours in Western cultures. However, it is a particularly perilous period for adolescents with ADHD as they may take these actions too far. A recent study of the everyday lives of adolescents with ADHD found that:

"ADHD characteristics were associated with behavioral patterns and contexts that may promote peer deviancy training, unhealthy lifestyle behaviors, and vulnerability to nicotine dependence." 25

Specifically, this study25 revealed that compared to their non-ADHD counterparts, adolescents with ADHD (and those who exhibited symptoms but did not meet criteria for a full diagnosis) reported:

  • more frequent negative moods (for example, higher rates of anger, anxiety, stress, and sadness)
  • lower rates of happiness, alertness, and well-being
  • less time with family and more time with friends
  • more time pursuing entertainment than achievement-oriented activities
  • more tobacco and alcohol use

Moreover, growing evidence indicates that adolescents with ADHD are at significant risk for a number of adverse outcomes compared to their non-ADHD peers, including:

  • lower academic achievement
  • less formal schooling (they leave school approximately two years earlier)26
  • higher rates of tobacco use (an adolescent with ADHD is three times more likely to be a daily smoker) and beginning smoking earlier25 17-28
  • substance abuse and antisocial behaviour29
  • teen pregnancy30-31
  • higher rates of adverse outcomes while driving (traffic citations, motor vehicle crashes in which they are at fault)32

ADHD in college students

Special education and disability laws in the U.S.A. and Canada have enabled many qualified students with disabilities (such as specific learning disabilities, ADHD, and other psychiatric disorders) to graduate from high school programs and enroll in post-secondary education programs in colleges and universities. For example, a recent survey of university students in the U.S.A. and other countries indicated that 2.9% of male students and 3.9% of female students report significant ADHD symptoms that would be consistent with a diagnosis of ADHD.33

On the one hand, these findings are encouraging because they indicate a positive outcome for a substantial proportion of students with ADHD. On the other hand, it is clear that college life poses more challenges to students with ADHD compared to those without disabilities. Problems typically experienced by young people with ADHD are often compounded by college living conditions, which may mean a dramatic change in the student's access to familiar support systems such as family, peers, teachers, and the structure of high school. Life in a university residence hall is often full of distractions, crowded, and noisy; there may be very little privacy and few quiet places.

College students may handle their problems associated with ADHD in different ways:34-37

  • "Fresh start": these students do not disclose their diagnosis of ADHD since they feel no-one at college will know them and/or that they no longer have problems. They may abandon all forms of treatment that helped them gain entry into the college, deny or fail to recognize that they are running into problems, and resist seeking help from student support services.
  • "Uninformed, unprepared": these students have also been diagnosed prior to college and may have been receiving pharmacological treatment, but they have no understanding how ADHD affects them, how it might impact on their college life, or how medication and other treatment help their ADHD symptoms.
  • "De novo ADHD": prior to college entry, these students have never been diagnosed with ADHD. They have been able to cope despite their symptoms, and have reached this level of academic achievement with tremendous effort and a supportive environment. However, during college they become overwhelmed by the level of independent functioning that is required and suddenly realize that something is amiss.

Impediments to success at the college level include issues that are both academic and/or personal. In particular, it appears that ADHD leads to poorer college adjustment by lowering self-esteem, which in turn results in poorer adjustment.35

Academic issues may include:

  • taking on too heavy a course load, due to problems estimating the multiple demands on one's time
  • poor organization and time management skills, which may result in "crash and burnout" (staying up all night and sleeping all day after studying, partying, or both)
  • reading problems resulting from difficulty concentrating and focusing, inability to read fast, and the frequent need for re-reading to be able to recall what has just been read
  • poor note-taking or writing skills, resulting in course failure, low marks, and a low grade point average

Personal issues may include:

  • high frustration levels or poor self-esteem
  • inappropriate social skills or too much time socializing
  • procrastination and problems persevering at a task
  • lack of sleep and difficulty getting up in the morning

Teachers in high school are well-positioned to play a substantial role in helping college-bound students with a diagnosis of ADHD prepare for the transition from secondary to post-secondary education.

ADHD in adults

Some individuals with ADHD continue to be inattentive, disorganized, impulsive, and moody in adulthood. Although adults with ADHD can demonstrate significant success in life, research has shown that adults with ADHD are at risk for a range of negative outcomes.8 37-42 Compared to their non-ADHD counterparts, adults with ADHD tend to:

  • make significantly less income and experience higher stress levels than a non-ADHD adult with similar levels of education
  • have lower ranking occupations
  • have greater emotional and social problems
  • have higher divorce rates
  • have a less positive self-image

Further, adults with ADHD may have greater difficulty in the role of parent, especially if they are parenting one or more children who also have ADHD.43 Some parents with ADHD may find it difficult to stick to schedules and routines and/or may find it difficult to squeeze more into their daily routines.

From a teaching perspective, parents with ADHD may pose challenges to the communication between home and school (see Table 2-1).

Table 2-1: Possible Challenges Communicating with Parents who Have ADHD44

Inattention Impulsiveness/hyperactivity Other problems related to ADHD
  • May forget to sign their child's planner, permission slips, or homework
  • May miss parts of the conversation during parent-teacher interviews
  • May not follow through on an agreed plan between the school and home
  • May come late or on the wrong day to parent-teacher meetings
  • May dominate the conversation or frequently interrupt parent-teacher interviews
  • May tap pencil, fidget, or shift position frequently during parent-teacher interview
  • May appear impatient, irritated, or uninterested
  • May treat every incident involving their child as a major crisis
  • May fail to modulate voice or tone during parent-teacher interview (that is, may sound angry, irritated, accusatory, etc.)

The following suggestions have been proposed for teachers working with parents who may have ADHD:44

  • Be nonjudgmental and only discuss the types of behaviours (academic or social) that are hindering the child's performance in the classroom.
  • Remember that the symptoms of ADHD are not "bad" but rather they interfere with learning and the student's academic success.
  • Provide parents with a written or brief oral summary of key points of a meeting and review keys steps to action plans.
  • Ask parents for information about what they do to help the child at home (for example, strategies that work) or information about the types of activities that the child seems to be able to enjoy.
  • Work together as a team. Create structures that help both you and the parents in dealing with common situations (for example, returning books or notes). Ask parents what would be best for them or what would fit within their existing routines.
  • If parents are interested, direct them to resources (such as community resources, books, and web sites) that can provide them with more information about parenting a child with ADHD.

ADHD is not a new disorder

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Demands of modern society do not cause ADHD. In fact, ADHD was first described in the mid-1800s by a German physician and children's storybook author, Dr. Heinrich Hoffman.45 Among his fictional characters, based loosely on actual patients from his clinic, were two that illustrate the same symptoms of ADHD described today. "Fidgety Phil" displayed hyperactive/impulsive symptoms, while "Johnny Head-in-the-Air" exhibited inattention symptoms.

Medical science first documented children exhibiting inattentiveness, impulsivity, and hyperactivity in 1902.46 Since that time, the disorder has been given numerous names by medical specialists, including minimal brain dysfunction, hyperkinetic reaction of childhood, and attention-deficit disorder with or without hyperactivity. The latter category was known as "ADD." While some people, including many professionals, still use the label "ADD" (attention-deficit disorder), this term is outdated and not recommended. For those who may have been diagnosed with ADD, the corresponding diagnostic category, using the Diagnostic and Statistical Manual for Mental Disorders, Fourth Edition (DSM-IV) classification system, would most likely be "ADHD, Predominantly Inattentive Type."47

Junk food and sugar intake do not cause ADHD

There is no scientific evidence to prove that eating sugar and/or junk food will cause ADHD.48 49 While recent evidence indicates that food additives are associated with higher activity levels, this behaviour occurs in all children and does not indicate a true "cause" of ADHD. ADHD symptoms persist regardless of the quality of the child's diet. There is little scientific evidence to indicate that dietary treatments alleviate symptoms of ADHD or improve academic functioning.50-52 In contrast, school-based interventions that focus on providing academic and behavioural support, according to a child's individual need, can facilitate reductions in behavioural symptoms and improve academic achievement.53-58

However, several factors have been implicated in ADHD and may play a causal role. These include genes, environmental factors, and altered brain functioning.

Genetic and environmental factors play a causal role in ADHD

Although ADHD is recognized in the medical field as an important clinical problem, its causes and its pathophysiology are not yet understood. ADHD is a complex neurobiological condition and both genetic and environmental factors are thought to play a causal role.

ADHD runs in families and is highly heritable

The first hint that genetic factors may play a role in ADHD came from research findings indicating that ADHD runs in families.59 For instance, compared to their non-ADHD peers, students with ADHD are two to eight times more likely to have at least one sibling with ADHD and to have a parent with ADHD, although the symptoms of ADHD may never have been identified or formally diagnosed in the family members.

Family studies cannot separate the effect of genes from possible environmental factors. To directly estimate the heritability of ADHD, twins need to be studied. Monozygotic ("identical") twins share 100% of their genes, whereas dizygotic ("fraternal") twins, like other siblings, share about 50% of their genes on average. Researchers determine the extent to which identical twins are concordant for ADHD (that is, the chance that if one twin has ADHD, the other will as well) and compare this to the rate in fraternal twins. From this information, researchers can then compute the heritability of ADHD, or the degree to which variability in ADHD in the population can be accounted for by genes. The mean heritability estimate for ADHD across about 20 twin studies is roughly 80%, indicating that ADHD is highly heritable — almost as heritable as height!60

From the school perspective, these findings mean that if a student with ADHD has siblings, one or more of the other siblings are likely to also have ADHD. But siblings with ADHD may show very different profile of ADHD symptoms and also may have different types of problems at school (for example, one sibling may have concurrent reading disabilities, whereas the other sibling may have additional problems with aggression or non-compliance). Thus, what worked for teaching and managing classroom behaviour for one of the siblings may not be effective with the other; a functional assessment of each student's strengths and difficulties is always required. It is also possible that one of the parents of the student with ADHD may have ADHD themselves. ADHD in adulthood poses additional challenges for parenting, particularly if both parent and child have ADHD (this issue was discussed in the section on ADHD in adults).43 61

Genetic factors in ADHD

The high heritability of ADHD has stimulated investigations into the molecular genetic basis of ADHD.60 62 Converging evidence from pharmacological, neuroimaging, and animal research has focused the molecular genetic research primarily on genes involved in specific neurotransmitter systems, particularly the dopamine system. At the time this website was created, there have been only a few genome-wide scans and no specific chromosomal region has been implicated unequivocally.62 Nonetheless, considerable progress has been made and several genes have been identified that increase the susceptibility to ADHD, including the dopamine D4 receptor gene (DRD4), the dopamine transporter gene (DAT1), and the dopamine D5 receptor (DRD5), as well as genes associated with the other neurotransmitters (noradrenaline, serotonin), and synaptosomal proteins, such as the SNAP-25 protein. However, these genes confer only a small additional risk of ADHD on their own and the general belief is that this complex disorder involves multiple genes of small to moderate effect. Researchers are now beginning to investigate how such genes work together and how they interact with environmental factors to influence behaviour. Researchers are also trying to identify patterns of genetic variation that may make it possible to develop individually tailored pharmacological treatments for this disorder.63

Environmental factors contribute to ADHD

Twin studies indicate not only that ADHD is highly heritable, but also that 10% to 25% of the variance in the ADHD phenotype is accounted for mostly by non-shared environmental factors, and that shared environmental factors play only a small role in increasing the risk for ADHD.64

Pregnancy, labour and delivery, and neonatal complications are associated with an increased risk for ADHD in childhood.65 Problems in the neonatal period, such as the need for an incubator, oxygen therapy, or surgery, are more common in children with ADHD than in their siblings, suggesting that neonatal complications may be a non-shared environmental risk factor.66 Other perinatal problems (that is, problems relating to the period around childbirth, especially the five months before, during, and one month after birth), such as prenatal exposure to nicotine or alcohol, prematurity, and low birth weight, are also associated with increased risk for ADHD and academic difficulties.67-68 For example, children of mothers who smoke during pregnancy are more likely to be rated by parents and teachers as exhibiting symptoms of inattention (or ADHD) and to exhibit lower academic achievement and poorer visuo-spatial reasoning.69-71 Also, children with ADHD are 2.5 times more likely to have been exposed to alcohol in utero and 2 times more likely to be exposed prenatally to cigarette smoke than non-ADHD control subjects.65 Moreover, maternal smoking during pregnancy is associated with lower levels of specific neurotransmitters (such as dopamine) in the fetus and elevated risk for subsequent nicotine dependence in adulthood in the offspring.72-74 However, the link between maternal smoking in pregnancy and increased risk for ADHD in the offspring may be shared family risks that interact to some degree with genetics.

Some toxic chemicals in the environment are known to interfere with the same aspects of behaviour and learning that are atypical in ADHD, and so are also thought to play a causal role.75-76 Lead is the best-studied example of an environmental contaminant that interferes with learning. Exposure to lead causes reductions in IQ and has also been linked to reading and learning disabilities, disruptive behaviour in the classroom, and reduced ability to pay attention. Lead exposure is also associated with increased risk for antisocial and delinquent behaviour in childhood and is a predictor of adult criminality.

Other toxic chemicals that have been shown to interfere with children's learning are the polychlorinated biphenyls (PCBs), chemical insulators that were widely used by industry until their ban in the U.S. in 1976 and that persist in the environment and in human tissue. Children are exposed to PCBs through breast milk and by eating fish and other fatty foods that contain high concentrations of PCBs. Children can also be exposed in utero, as PCBs move across the placenta. Exposure to high levels of PCBs has been shown to interfere with many aspects of cognitive development, including lower full-scale and verbal IQ scores as well as significant attention and memory deficits.75

Brain Differences in ADHD

Recent advances in human brain neuroimaging techniques, which provide visual images of the brain's structure and function, are providing important insights into subtle but important brain differences in individuals with ADHD.77-79

To date, one of the largest investigations of brain structure difference in children with and without ADHD took place over a 10-year period.80 At various ages during this time, children's brains were scanned using a brain imaging technique called magnetic resonance imaging (MRI).42 The researchers found that the brains of boys and girls with ADHD were 3% to 4% smaller than those of children without ADHD. In addition, the researchers found that the more severe the symptoms of ADHD (as rated by clinicians and parents), the smaller were the children's frontal lobes, temporal gray matter, caudate nucleus, and cerebellum. These brain regions are involved in the ability to concentrate; they also regulate impulse control, motor activity, and inhibition — all characteristic problem areas for individuals with ADHD. The researchers also found that the course of brain development in children with and without ADHD was similar, suggesting that whatever caused the alterations in the brain occurred early in development.

Excitingly, a neuroimaging technique called functional MRI enables researchers to measure brain activation patterns while children are performing various cognitive tasks. For example, studies have shown that the specific reductions in brain volume in individuals with ADHD are associated with poorer performance on tests of attention and inhibition as well as measures of behaviour.77-78 81-83 Moreover, another new neuroimaging technique, called diffusion tensor imaging (DTI), is allowing scientists to look at the white matter (composed of nerve fibres) in children's brains in more detail to help explain the physical differences in the brain regions described above. A recent study using DTI found abnormalities in the fibre pathways in the frontal cortex, corpus striatum, brainstem, and cerebellum — areas that are involved in regulating attention, impulsive behaviour, motor activity, and inhibition, which are all related to ADHD symptoms.84 These findings suggest that there may be abnormalities not just in one or two areas of the brain in individuals with ADHD, but in specific brain circuits that connect the front and back of the brain.

Figure 2-2 lists (albeit simplistically) the brain regions that have been found to be altered in ADHD, along with the type of cognitive functions that these brain regions support. Inevitably, further advances in neuroimaging techniques will alter our understanding of brain functioning in ADHD. Importantly, there is no evidence to date that indicates that treatment with stimulant medication causes the brain abnormalities observed in ADHD.80 Nonetheless, our existing knowledge suggests that brain abnormalities likely contribute to or even account for the behavioural symptoms and cognitive problems of individuals with ADHD.

Figure 2-2: Brain Differences in ADHD

Summary

The causes of ADHD and its various features are complex and multifactorial. To date, there is no specific test for ADHD; there is no blood test, genetic test, psychological test, or brain scan that can determine whether an individual has ADHD or has an increased risk for developing ADHD. However, the research findings clearly indicate that ADHD is a neurobiological disorder. Scientists believe that genetic and environmental factors give rise to the subtle brain alterations in ADHD, which in turn underlie both the behavioural and learning problems that are characteristic of individuals with ADHD.

Learning problems are intrinsic to ADHD

Currently, ADHD itself is not believed to constitute a specific learning disability by medical, educational, or legal bodies, although they do recognize that at least one-third of children with ADHD will meet existing criteria for a learning disability. By contrast, growing neuroscientific evidence from brain studies of children and adolescents with ADHD suggests that learning problems are an integral feature of ADHD. These cognitive and learning problems are discussed in more detail in Chapters 3 and 4.

Educational implications for the classroom

Given the chronic and impairing nature of ADHD, it is important for intervention efforts to be comprehensive and initiated over the long-term.

  • A team approach, with clear communication between team members (home, school, other professionals), is strongly advocated.
  • Early identification of a child's learning needs, strengths, and behavioural difficulties will help identify the instructional targets (for example, literacy skills) and supports necessary to enhance engagement and learning.
  • Adolescents with ADHD may need a range of educational support systems and health promotion activities to reduce the risk for adverse outcomes.

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